Typically, dermatological liquid injection apparatuses indicate apparatuses for injecting a tattooing pigment of a needle unit into the skin or for injecting liquid or gel medicine applied to an affected area of the skin, into the skin.
Such a liquid injection apparatus fabricates a needle unit including a disposable needle for bacterial infections, and mounts the needle unit to a front end of the liquid injection apparatus to use it.
However, although a conventional liquid injection apparatus uses the disposable needle unit, blood and liquid mixture oozing out of the skin frequently flows into a body of the liquid injection apparatus along the disposable needle unit because of the needle during a medical procedure. Since the connection between the needle unit and the main body has a mere mechanical connection structure and cannot block the small amount of the blood flowing into the body, the blood and the liquid mixture of the previously operated person remains in the main body after the liquid injection apparatus is used. Accordingly, it is hard for the conventional liquid injection apparatus to thoroughly block the bacterial infection even when the disposable needle unit is used.
In addition, in the conventional liquid injection apparatus, the needle is guided by a through hole of a cap unit coupled to the main body front end to reciprocate. At this time, the medicine or the tattooing pigment is discharged in the small amount between a needle outer circumference and the through hole. However, when the part between the needle outer circumference and the through hole is clogged in the medical procedure, the supply of the medicine or the pigment is stopped. In this case, it is necessary to replay with a new needle unit.